so by that measure all high sided lorries should be off the road at the same time then? surely one of them being blown about is more dangerous to more people .
Well yes, there is a case for keeping high sided lorries off the road (they are banned from certain bridges when wind speeds are dangerously high). Unfortunately this may conflict with our 'just in time' economic systems which require goods to be at a particular place at a particular time, so it may not be possible/feasible/practical to ban them from the roads for hours at a time.